Projection systems have been used for many years to project motion pictures and still photographs onto screens for viewing. More recently, presentations using multimedia projection systems have become popular for conducting sales demonstrations, business meetings, and classroom instruction.
In a common operating mode, multimedia projection systems receive analog video signals from a personal computer (“PC”). The video signals may represent still, partial-, or full-motion display images of a type rendered by the PC. The analog video signals are typically converted in the projection system into digital video signals, and the signals are electronically conditioned and processed to control an image-forming device, such as a liquid crystal display (“LCD”) or a digital micromirror display device (“MDD”).
A popular type of multimedia projection system employs a broad spectrum light source and optical path components upstream and downstream of the image-forming device to project the image onto a display screen. An example of a MDD-based multimedia projector is the model LP420 manufactured by in Focus Systems, Inc., of Wilsonville, Oreg., the assignee of this application.
Significant effort has been invested into developing projectors producing bright, high-quality, color images that are also compact so that they can be portable. However, it is desirable to further decrease the size and weight of such projectors. Furthermore, conventional projectors, which use high pressure mercury arc lamps, have lamp lifetimes of roughly 2000 hours. It is desirable to use a light source with lifetime in excess of 10,000 hours so that the user need not worry about failure of the projector or the cost and effort of lamp replacement.
An alternative optical architecture is, therefore, desired that substantially decreases the size and weight of the projection system as compared with conventional projection systems and significantly enhances light source lifetime.